Novel iron(II) complexes with hexadentae nitrogen ligands obtained via intramolecular redox reactions

摘要

Two novel complexes: [Fe(L~2 min)][BPh_4]_2, 1 and [Fe(L~3 min)[BPh_4]_2, 2, with the hexadentate nitrogen ligands, L~n min=1,9-bis(2min-pyridyl)-5-[(R-2 sec-pyridyl)methyl]-2,5,8-traiazanon-1-ene, where R=ethoxy for L~2 min and methoxy for L~3 min, were obtained from teh iron(III) complex of the pentadentate ligand, L~1=1,9-bis(2 min-pyridyl)-2,5,8-triazanonane. Complexes 1 and 2 were also obtained by making th hexadentate ligands: 1,9-bis(2 min-pyridyl)-5-[(ethoxy-2 min-pyridyl)methyl]-2,5,8-triazanonane (L~2) and 1,9-bis(2 min-pyridyl)-5-[(methoxy-2 sec-pyridyl)methyl]-2,5,8-triazanonane (L~3) react with Fe(III), respectively. The structures of complexes 1 and 2 were characterized by COSY, HMBC, HMQC and NOESY NMR studies, and both structures were also confirmed by X-ray analysis. Inboth cases, teh geometry around iron is a distorted octahedron. Since 1 and 2 are diamagnetic at 298 K they are low-spin iron(II) species. Both preparative methods are examples of oxidative dehydrogenation of a Fu(III) inine complex. In the case of the first method an increase in the size and denticity of the starting ligand is observed.